At a very early age, children learn how to classify objects according to their shape. Now, new research suggests studying the shape of the aftermath of supernovas may allow astronomers to do the same.

A new study of images from NASA's Chandra X-ray Observatory on supernova remnants — the debris from exploded stars — shows that the symmetry of the remnants, or lack thereof, reveals how the star exploded. This is an important discovery because it shows that the remnants retain information about how the star exploded even though hundreds or thousands of years have passed.

"It's almost like the supernova remnants have a 'memory' of the original explosion," said Laura Lopez of the University of California at Santa Cruz, who led the study. "This is the first time anyone has systematically compared the shape of these remnants in X-rays in this way."

Astronomers sort supernovas into several categories, or "types", based on properties observed days after the explosion and which reflect very different physical mechanisms that cause stars to explode. But, since observed remnants of supernovas are leftover from explosions that occurred long ago, other methods are needed to accurately classify the original supernovas.

Lopez and colleagues focused on the relatively young supernova remnants that exhibited strong X-ray emission from silicon ejected by the explosion so as to rule out the effects of interstellar matter surrounding the explosion. Their analysis showed that the X-ray images of the ejecta can be used to identify the way the star exploded. The team studied 17 supernova remnants both in the Milky Way galaxy and a neighboring galaxy, the Large Magellanic Cloud.

For each of these remnants there is independent information about the type of supernova involved, based not on the shape of the remnant but, for example, on the elements observed in it. The researchers found that one type of supernova explosion — the so-called Type Ia — left behind relatively symmetric, circular remnants. This type of supernova is thought to be caused by a thermonuclear explosion of a white dwarf, and is often used by astronomers as "standard candles" for measuring cosmic distances.

On the other hand, the remnants tied to the "core-collapse" supernova explosions were distinctly more asymmetric. This type of supernova occurs when a very massive, young star collapses onto itself and then explodes.

"If we can link supernova remnants with the type of explosion", said co-author Enrico Ramirez-Ruiz, also of University of California, Santa Cruz, "then we can use that information in theoretical models to really help us nail down the details of how the supernovas went off."

Models of core-collapse supernovas must include a way to reproduce the asymmetries measured in this work and models of Type Ia supernovas must produce the symmetric, circular remnants that have been observed.

Out of the 17 supernova remnants sampled, ten were classified as the core-collapse variety, while the remaining seven of them were classified as Type Ia. One of these, a remnant known as SNR 0548-70.4, was a bit of an "oddball". This one was considered a Type Ia based on its chemical abundances, but Lopez finds it has the asymmetry of a core-collapse remnant.

"We do have one mysterious object, but we think that is probably a Type Ia with an unusual orientation to our line of sight," said Lopez. "But we'll definitely be looking at that one again."

While the supernova remnants in the Lopez sample were taken from the Milky Way and its close neighbor, it is possible this technique could be extended to remnants at even greater distances. For example, large, bright supernova remnants in the galaxy M33 could be included in future studies to determine the types of supernova that generated them.

The paper describing these results appeared in the November 20 issue of The Astrophysical Journal Letters. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

More information, including images and other multimedia, can be found at:

Visitor Comments (15)

Is there any expected difference in the remenant of a type 1a in the 2 main projenator scenarios Ie can you tell if the type 1a resulted from accretion from another star or from 2 white dwarfs merging
If not why not? Surely a merger would give a much less symmetric remnant.

Posted by Jon on Sunday, 11.23.14 @ 09:20am

Good and clear explanation. Easy to understand.

Posted by Amanda on Wednesday, 11.19.14 @ 08:30am

Marvelous job. Hats off to the scientists involved.

Posted by Souvik Biswas on Monday, 02.7.11 @ 00:17am

These pictures are amazing and they bring my attention to a whole new universe.

Posted by Meghan on Thursday, 03.4.10 @ 11:30am

The pictures are amazing.

Posted by lizette garcia on Thursday, 01.21.10 @ 17:28pm

This is very interesting, there is so much to see.

Posted by jenny on Thursday, 01.14.10 @ 10:57am

Excellent work, keep it up as the whole world benefits by learning how the universe works.

Posted by Barry Weseen on Sunday, 12.27.09 @ 16:18pm

Fabulous graphics and insights on an extraordinary event.

Posted by Dave on Saturday, 12.19.09 @ 19:10pm

Thanks so much. I have learned something new about Novas in general. It is so mind boggling, I get dizzy thinking about all this. There is so much to learn about this great universe we live in.

Posted by Marvin L. S. on Saturday, 12.19.09 @ 18:53pm

This is very nice. Good luck to the scientists. Give us more.

Posted by charles on Saturday, 12.19.09 @ 02:04am

More excellent images.
Very fine detail, and an elegant idea applied to great effect.

Posted by Mark Ballington on Friday, 12.18.09 @ 10:17am

Very good.

Posted by sicre on Friday, 12.18.09 @ 07:08am

Is there any indication of some vague gravitational wave behavior accompanied this discovery? Or it is too late to judge.

Posted by Magd Kahil on Thursday, 12.17.09 @ 23:34pm

Very informative article. As usual you continue to educate me in my interest in cosmology, although I remain a novice. Thank you

Posted by Rich on Thursday, 12.17.09 @ 18:16pm

Cool

Posted by DAVID on Thursday, 12.17.09 @ 17:23pm

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